Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true and destructiveHint=false; the description is consistent, framing the operation as verification/reporting. It adds useful context about key sources (Authorization header vs. trial api_key) and clarifies the trial/permanent key distinction, which goes beyond annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is two sentences, direct and front-loaded with the purpose. It doesn't waste words, covering purpose, usage context, and key requirements in a compact form.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a diagnostic tool with one optional parameter and no output schema, the description tells what it checks (plan, balance, usage), when to use it, and how to provide the key. It doesn't specify the response format, but the content is adequately covered, and sibling tools are clearly unrelated.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The single parameter api_key already has a detailed schema description stating it's only for temporary keys. The tool description repeats this but adds context about the Authorization header. With 100% schema coverage, the description adds marginal value beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool verifies an API key and reports plan, credit balance, and recent usage. This is a specific verb+resource pair that distinguishes it from sibling tools like oruk_transcribe_audio or oruk_list_models.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It explicitly says 'Use this as the first call after setup' and 'when a billing/auth error needs diagnosing,' giving concrete when-to-use context. However, it doesn't explicitly name alternative tools or state when not to use it, so it falls short of a full 5.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.